A typical method for forming medical device balloons includes molding the balloon from a tubular balloon parison, such as an extruded tubular balloon parison, in a mold during a blow molding process. During the blow molding process, the mold is heated to elevate the temperature of the polymeric material (e.g., thermoplastic material) of the balloon parison in order to soften the polymeric material. While the balloon parison is at an elevated temperature, the interior of the balloon parison is pressurized to expand the softened polymeric material within the cavity of the mold such that the polymeric material conforms to the shape of the cavity to form the inflatable balloon. During a subsequent manufacturing process, the formed balloon is bonded to a catheter shaft to form the balloon catheter (e.g., the balloon waists are bonded to the catheter shaft after the balloon is blow molded).
Other medical device balloons are formed by dipping a balloon-shaped mandrel in a bath of liquid material or polymer. When dried, the liquid material or polymer forms a skin around the mandrel which can be removed and used as a balloon. For example, latex balloons are produced using this method.
In some instances, it may be difficult to secure a previously formed inflatable balloon to a catheter shaft during a subsequent balloon bonding process. For example, in some applications it may be desirable to provide the balloon catheter with no distal tip extending distal of the balloon. In such instances, the distal waist of the inflatable balloon may be inverted and bonded to the outer surface of the catheter shaft in an inverted orientation, thus positioning an inflatable portion of the balloon at or distal of the distal extremity of the catheter shaft. One such balloon catheter, configured for directing a re-entry device back into the true lumen during a subintimal recanalization procedure, is disclosed in U.S. Pat. No. 8,257,382, the disclosure of which is incorporated herein by reference. Other procedures in which a balloon catheter without a distal tip extending distal of the balloon may be advantageous include angioplasty, ablation, neuromodulation, kyphoplasty, and sinuplasty, for example. Inverting the balloon waist and/or securing the inverted balloon waist to the catheter shaft after the balloon blowing step is difficult and time consuming.
Accordingly, it is desirable to provide alternative methods of forming a balloon catheter and the resultant balloon catheter, such as a balloon catheter with an inflatable balloon having a proximal and/or distal inverted waist bonded to a component of the catheter shaft.